Oct 15, 2009 · May I know what ?= means in a regular expression? For example, what is its significance in this expression: (?=.*\\d).

Be aware that the first ^ in this answer gives the regex a completely different meaning: It makes the regular expression look only for matches starting from the beginning of the string.

In case it is JS it indicates the start and end of the regex, like quotes for strings. stackoverflow.com/questions/15661969/…

Oct 3, 2010 · Now, when the regex engine tries to match against aaaaaaaab, the .* will again consume the entire string. However, since the engine will have reached the end of the string and the pattern is …

Normally the dot matches any character except newlines. So if .* isn't working, set the "dot matches newlines, too" option (or use (?s).*). If you're using JavaScript, which doesn't have a "dotall" option, …

Dec 8, 2018 · The regex compiles fine, and there are already JUnit tests that show how it works. It's just that I'm a bit confused about why the first question mark and colon are there.

Apr 7, 2011 · I'm reading the regular expressions reference and I'm thinking about ? and ?? characters. Could you explain me with some examples their usefulness? I don't understand them enough. thank …

By putting ^ at the beginning of your regex and $ at the end, you ensure that no other characters are allowed before or after your regex. For example, the regex [0-9] matches the strings "9" as well as …

Aug 7, 2008 · Regex Syntax Summary How Regexes Work JavaScript Regular Expressions Footnote †: The statement above that . matches any character is a simplification for pedagogical purposes that is …

Jan 2, 1999 · Parentheses in regular expressions define groups, which is why you need to escape the parentheses to match the literal characters. So to modify the groups just remove all of the unescaped …